Dot matrix printers presently in use employ ink as the printing means and are typically designed in accordance with one of the two following concepts:
(1) Directly applying ink to the print receiving material to form the specified character. Such printers are typically referred to as "ink jet printers," as shown, for example, in U.S. Pat. No. 3,281,859.
(2) Transferring ink contained within an ink carrying medium such as a fiber ribbon saturated with ink and positioned adjacent to the print receiving material whereby transfer occurs by impacting the inked ribbon against the ink receiving material. Printers of this type are generally referred to as "impact type printers." One typical printer of the dot matrix type is shown in U.S. Pat. No. 3,833,105, assigned to the assignee of the present application.
These two basic designs have a number of disadvantages, some of the more significant ones being:
(1) The ink jet method of printing is complicated, expensive, and cannot be used to print on multiple ply print receiving material.
(2) The complex and delicate nature of ink jet printers require constant maintenance and the concept employed requires constant generation of a stream of ink dots, even when not printing at selected positions on the ink receiving material, causing a great deal of wasteful employment of unused ink and requiring a complex collection and recirculation means.
(3) In impact printers employing inked ribbons, the print density and quality is non-uniform as usage of the ribbon increases, especially due to the non-uniform manner in which ink is transferred from the ribbon to the ink receiving material. This is due to the extraction of the ink by the constant impact of the print wires. The ink is extracted from the ribbon up to the point where characters being printed become illegible and the ribbon must therefore be changed.
(4) The ribbon manufacturing process is costly and complicated and many of its associated problems affect the life and performance of the ribbon.
(5) Inked ribbons must be changed frequently. The changing operation is time-consuming and messy.
(6) Printers employing inked ribbons must be provided with complicated mechanical assemblies necessary for guiding and moving the ribbon between the print head and the print medium, further adding to the maintenance, cost and problems of the printer.
(7) Due to the short life of inked ribbons some designs provide for re-inking of the ribbon while in use on the printer. Such operations are costly, have low efficiency, and are greatly affected by the environmental conditions as well as the ribbon fabric to the extent that any adverse condition will destroy whatever gains might be available through the use of the re-inking process.